[Anhedonia in mood disorders and somatic diseases: results of exploratory Mendelian randomization analysis]

To conduct an exploratory Mendelian randomization analysis of the causal relationships of anhedonia with a wide range of psychiatric and somatic phenotypes based on the genetic data of participants in a population study.

This cross-sectional study included 4520 participants, of which 50.4% (n=2280) were female. The mean age was 36.8 (S.D.=9.8) years. Participants were pheno-nailed based on the DSM-5 criteria for anhedonia in the framework of depression. An episode of anhedonia exceeding 2 weeks during life was reported by 57.6% (n=2604) of participants. A genome-wide association study (GWAS) of the anhedonia phenotype was performed, as well as a Mendelian randomization analysis using summary statistics of large-scale GWASs on psychiatric and somatic phenotypes.

The GWAS on anhedonia did not reveal the variants with genome-wide significant association (p<10^-8). The most significant (p=9.71×10^-7) was the variant rs296009 (chr5:168513184) in an intron of the slit guidance ligand 3 (SLIT3) gene. Using Mendelian randomization, nominally significant (p<0.05) causal associations of anhedonia with 24 phenotypes were identified, which can be divided into 5 main groups: psychiatric/neurological diseases, inflammatory diseases of the digestive system, respiratory diseases, oncological diseases and metabolic disorders. The most significant causal effects of anhedonia were found for breast cancer (p=0.0004, OR=0.9986, 95% confidence interval (CI) (0.9978-0.999)), minimal depression phenotype (p=0.009, OR=1.004, 95% CI (1.001-1.007)), as well as for apolipoprotein A (p=0.01, OR=0.973, 95% CI (0.952-0.993)) and respiratory diseases (p=0.01, OR=0.9988, 95% CI (0.9980-0.9997)).

The polygenic nature of anhedonia may cause the risks of comorbidity of this phenotype with a wide range of somatic diseases, as well as may be associated with mood disorders.